IC package with power and signal lines on opposing sides

ABSTRACT

A package for integrated circuits is described. The package has a package substrate with a land side and an opposite die side, a first set of low level signal connectors on the die side to connect to an IC to be carried by the package, and a second set of low level signal connectors on the die side to connect to external components. The package may have power connectors on the land side or a power supply attached to the land side. A heat spreader or cooler may be attached to the die side.

BACKGROUND

1. Field

The present description relates to integrated circuit packaging, andmore particularly, to the placement of external connections on anintegrated circuit package.

2. Background

IC's (Integrated Circuits) are manufactured in and on semiconductorwafers with several layers of active circuitry. The wafer is cut intoseparate semiconductor chips or dies which are mounted to andelectrically coupled to package substrates. The substrates and dies aresealed inside a package for which the substrate is said to be on theland side of the package and the chip or die is said to be on the dieside of the package. Pins, balls or lands for the ground plane, powerplane and low level signaling extend from the package to allow thepackage to be coupled to a PCB (Printed Circuit Board), PWB (PrintedWiring Board), or a socket. Many packages also have a heat transferplate or some other heat conducting structure to connect to a coolingdevice such as heat fins, heat pipes, liquid radiators, etc.

Typically, all of the package connections for ground, power, andsignaling are placed on the land side of the package and extend directlyfrom the package substrate. For more complex chips, this requires thatthe connectors be very close together and that the high level powerconnectors be placed close to low level signal connectors. The die sidetypically has no connections except for cooling connections. Forexample, the die side of the package may carry a finned heat sink. Forhigher power chips, a fan with power and control connectors may also bemounted to the die side of the package.

The die operates best with a clean power supply and reference voltage,for example a uniform voltage level and minimal noise. The powerdelivery path from a power supply such as a VRM (Voltage RegulatorModule) to the die, however, has an inductance associated with it,creating impedance in the power delivery system. During core switching,when a portion of the microprocessor is powered up or powered down, alarge amount of current is drawn by the die and the current changecauses a large voltage drop at the die due to the inductance in thepower delivery path. These voltage drops may be mitigated usingdecoupling capacitors, but the capacitors add complexity and expense tothe system design. Some systems use bulk capacitors, die sidecapacitors, and on-die (or embedded chip) capacitors. Land sidecapacitors are also used in some systems.

In addition, the trend in processor design is to operate at lowervoltages (1 volt or less) but higher power, this increases the necessaryamperage (100 Amps or more). Higher current levels are more susceptibleto impedance effects and voltage drops. High current levels also requiremore bulky and expensive connectors between the VRM and associated chip.High current levels also create interference or distortion in low levelsignaling connections.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be understood more fully fromthe detailed description given below and from the accompanying drawingsof various embodiments of the invention. The drawings, however, shouldnot be taken to be limiting, but are for explanation and understandingonly.

FIG. 1 is a cross-sectional diagram of an IC package according to afirst embodiment of the invention;

FIG. 2 is a cross-sectional diagram of an IC package according to asecond embodiment of the invention;

FIG. 3 is a cross-sectional diagram of an IC package according to athird embodiment of the invention;

FIG. 4 is a cross-sectional diagram of an IC package according to afourth embodiment of the invention;

FIG. 5 is a cross-sectional diagram of an IC socket with a recessaccording to an embodiment of the invention;

FIG. 6 is a cross-sectional diagram of an IC socket with an openingaccording to an embodiment of the invention; and

FIG. 7 is a diagram of a computer system with a socket for use with thedescribed packages and sockets.

DETAILED DESCRIPTION

FIG. 1 is a cross-sectional diagram of an IC (Integrated Circuit)package coupled to a PCB (Printed Circuit Board). The package has an IC,die, or chip 11 attached to a package substrate 12. The IC may be any ofa variety of different types including a microprocessor,microcontroller, ASIC (Application Specific Integrated Circuit), FPGA(Field Programmable Gate Array), DSP (Digital Signal Processor), memory,I/O (Input/Output) controller or hub, etc. The substrate has data,control, and power interfaces 13 to the chip coupled to ground, powerand signaling planes within the substrate. The substrate may be formedfrom any rigid dielectric substrate, such as a standard PC (printedcircuit) board material, for example, FR-4 epoxy-glass, polyimide-glass,benzocyclobutene, Teflon, other epoxy resins, injection molded plasticor the like or ceramic. In one embodiment, the substrate is about 40mils (1.0 mm) thick although it may be thicker or thinner, in otherembodiments. The die is coupled to the substrate using a set ofconnectors 13, such as C4 (Controlled Collapse Chip Connect) bumps orany other type of electrical connection system.

The package includes a cover 14 attached to the package substrate. Thecover forms an internal enclosure for the die that is sealed against theexternal environment to protect the die. The cover may be hermeticallysealed to the substrate or it may surround the substrate. In oneembodiment, the cover is an IHS (Integrated Heat Spreader) glued to thepackage substrate and thermally coupled to the die to transfer heat fromthe die to the package exterior. However, other types of covers may alsobe used.

The package substrate 12 is coupled to a second substrate 15 which maybe a motherboard, a daughtercard, a cartridge substrate, a flexboard orany other substrate which may carry the package. In one embodiment, thesecond substrate is a conventional PCB, PWB (Printed Wiring Board) or asocket mounted to such a board. The die side of the package substrate ismounted to the second substrate using a set of connectors 16. Theseconnectors may include power, ground and signaling connectors or asubset of such connectors. The connectors may be implemented using anyof a variety of different technologies including BGA (ball grid array),SMT (Surface Mount Technology), LGA (Land Grid Array) or any of avariety of solder reflow technologies.

As shown in FIG. 1, the PCB 15 is spaced apart from the packagesubstrate 12. This allows room to accommodate the package cover and die.The spacing may be accomplished using a PCB material with vias toaccommodate connectors between the package substrate and the main PCB.The spacing may be accomplished by designing an appropriate socket.Alternatively, the connectors may provide the spacing. Elastomericmaterials may be used between the package substrate and the PCB withconductive columns through the elastomeric material to carry theconnections. Connector pins and receptacles may be used for theconnections designed so that the pins are long enough to provide thespacing. The electrical connection and the physical spacing may beprovided by the same structure as shown in FIG. 1 or by differentstructures.

In the example of FIG. 1, power may be supplied to the die eitherthrough the die side connectors or through other connectors. Forexample, low level data signals may be communicated on the die sideconnectors while power is provided through land side connectors (notshown). Alternatively all connections may be made through the die sideconnectors.

As can be seen in FIG. 1, the package substrate 12 couples the die 11 tothe PCB or socket 15. Since the die connectors 13 and the packageconnectors 16 are on the same side of the substrate, the die side, theinterconnections between the connectors do not have to penetrate throughthe entire thickness of the die. This allows the package substrate to beformed from a relatively thick material. A thick package substrate maybe lower cost, better insulating and more durable than a thinnersubstrate. For the die side connectors shown in FIG. 1, microtraces orlaser drilled vias of 30–40 μm or less may be used to interconnect theconnectors.

FIG. 2 is a cross-sectional diagram of an alternative IC package coupledto a PCB. The package has an IC, die or chip 21 attached to a packagesubstrate 22 using a set of connectors 23, such as C4 (ControlledCollapse Chip Connect) bumps similar to the diagram of FIG. 1. Thepackage includes a cover 24 to seal the die and protect it from theexternal environment.

The package substrate 22 is coupled on its die side to a secondsubstrate 25 such as a PCB using a set of connectors 26. Theseconnectors are low level signaling connectors coupled to the die throughshallows vias or microtraces as described above with respect to FIG. 1.

The land side of the package is coupled to a power supply 27 through aset of power connectors 28. The power connectors extend through thepackage substrate 22 to couple the die 21 directly to the power supply27. These interconnections penetrate through the entire thickness of thedie through drilled vias that may be 800 μm deep or more. This path isconsiderably shorter than a path across the PCB 25 to a power supplymounted adjacent the package. As a result, the path parasitics aregreatly reduced. This reduces or eliminates any need for decouplingcapacitors. The VRM may include capacitance in its voltage outputs thatis sufficient for reliable chip operation. In addition, by providingpower on one side of the package and low level signaling on the oppositeside of the package, distortion, interference, and cross talk in the lowlevel signaling is reduced.

The power supply may include a connector (not shown) to couple the powersupply to a main or primary power supply. In one embodiment, the powersupply is a VRM that receives a 12 volt supply from a main power supplyand converts it to multiple 1.4 volt supplies each to supply a differentcore of the chip. A single chip may have a single voltage input withVcc, Vss, and ground or it may have six or more cores each requiring thesame or different voltages. Because the VRM is coupled directly to thepackage it may be designed specifically for the particular chip inside.The VRM may be fastened to the package so that when the package isreplaced with another package, the VRM is also replaced in the sameoperation. Alternatively, instead of the power supply 27 shown, acoupling interface may be used to couple the connectors 28 to a powersupply located near the package.

The power connectors 28 may also include control lines to enable,disable and adjust each of the core voltages. Placing the VRM so closeto the die allows the control lines to change power settings veryquickly. This reduction in reaction times allows more precise control ofthe chip and also allows it to operate closer to its maximum speed andvoltage.

As an alternative, the PCB 25 may have a recess or depression that islarge enough to receive the package cover 24 or some portion of thepackage but not as deep as the PCB. By recessing the package into theopening, the die side connectors may be made much shorter. This reducesparasitics and simplifies the mounting process. The package mayalternatively be mounted to a socket and not directly to the PCB. Inthis case, the socket may include a hole or a recess to receive thepackage cover (see e.g. FIG. 5). Any desired cooling connections may beaccommodated by the socket or the PCB. So, for example, heat pipes orliquid tubing may extend through the socket to the IHS to carry heat tothe outside of the socket for ambient or refrigerant cooling. Similaralternatives may be applied to the embodiment of FIG. 1.

FIG. 3 is a cross-sectional diagram of another alternative IC packagecoupled to a PCB. The package has an IC, die or chip 31 attached to apackage substrate 32 using a set of connectors 33, such as C4(Controlled Collapse Chip Connect) bumps similar to the diagram ofFIG. 1. The package includes a cover 34, such as an IHS, to seal the dieand protect it from the external environment. In the example of FIG. 3,the cover is thermally coupled to the die using, for example, a TIM(Thermal Interface Material) such as a metal or polymer solder. Thecover may be plated or coated aluminum or copper or some other heatconductive material. One such cover is referred to as an IHS (IntegratedHeat Spreader).

The package substrate 32 is coupled on its die side to a secondsubstrate 35 such as a PCB using a set of connectors 36. Theseconnectors may include power, ground and low level signaling connectorscoupled to the die through planes or through shallow vias or microtracesas described above with respect to FIG. 1.

The example of FIG. 3 also includes a heat sink 39 thermally coupled tothe package cover or IHS using, for example a TIM (Thermal InterfaceMaterial) or a spring connector. The heat sink has a set of pins or finsto present a large surface area to the ambient air outside the package.The heat sink may be augmented by a fan or some other cooler, such asheat pipes, liquid coolers, etc.

In contrast to the PCB of FIGS. 1 and 2, the PCB of FIG. 3 includes anopening 30 which is large enough to receive the package cover. In theexample of FIG. 3, this hole 30 extends all the way through the PCB. Itmay take the form of a rectangular cut-out in the PCB material. Anyconnectors on the surface layer or other planes in the PCB may be routedaround the hole. When the die side connectors are coupled to the PCB,the IHS 30 extends through the PCB.

By recessing the package into the opening, the die side connectors maybe made much shorter. This reduces parasitics and simplifies themounting process. If the package is mounted to a socket and not directlyto the PCB, the socket may include a hole or a recess to allow a heatsink or other cooling device to be attached to the die side of thepackage, i.e. through the bottom of the socket (see e.g. FIG. 6). Anydesired cooling connections may be accommodated by the socket, such asfins as shown, heat pipes or liquid tubing which all may extend throughthe socket to the IHS to carry heat to the outside of the socket forambient or refrigerant cooling.

In the example of FIG. 3, the heat sink is attached to the IHS from theopposite side of the PCB. The IHS is almost as large as the opening inthe PCB and the heat sink is substantially larger than the PCB, however,the relative sizes of these components may be adapted to suit differentapplications. From a position on the opposite side of the PCB, the heatsink may connect to a different ambient environment than that of therest of the package. In a computer system embodiment, for example, thePCB may be a motherboard with sockets for memory and adapter cards onthe same side as the microprocessor socket. The heat sink on theopposite side of the motherboard may be exposed to dedicated fans, mayextend outside the computer case, or may be coupled to a portion of thecomputer system case or chassis.

FIG. 4 is a cross-sectional diagram of another alternative IC packagecoupled to a PCB. The package has an IC, die or chip 41 attached to apackage substrate 42 using a set of connectors 43 similar to the diagramof FIG. 1. The package includes a cover 44, such as an IHS to seal thedie and protect it from the external environment.

The package substrate 42 is coupled on its die side to a secondsubstrate 45 such as a PCB using a set of connectors 46. Theseconnectors are low level signaling connectors coupled to the die throughshallows vias or microtraces as described above with respect to FIG. 2.

The land side of the package is coupled to a power supply 47 through aset of power connectors 48, similar to that described with respect toFIG. 2. The power connectors extend through the package substrate 42 tocouple the die 41 directly to the power supply 47. As with the exampleof FIG. 2, the separation between the high current land side power linesand low current die side signal lines reduces the return and insertionloss for the signal lines and reduces cross talk between the power andthe signal lines. The very short distance between the power supply andthe die reduces voltage droops boosting efficiency and reducing heat.

The connected power supply also allows each package to be fitted with apower supply and any decoupling capacitors specifically adapted for theparticular die. The combination of die, package, VRM, decouplingcapacitors and heat sinks may be sold and shipped as a single unit. If apackage is replaced, then the specific power supply and other componentsmay be replaced in a single operation without replacing any other PCBcomponents.

The packages of FIGS. 1–4 may be mounted directly to a PCB or mounted ina socket which is, in turn mounted to a PCB. A suitable socket is showntogether with a package in FIG. 5. The socket 53 is shown incross-section to reveal a cut-out, opening or recess 55 within thesocket to receive the die 51 and cover or heat spreader 54 of the ICpackage 52. The recess is a structure that is designed to accommodatethe package. As shown in FIGS. 1–4, the package extends on the die sideaway from the die side connectors. The recess accommodates thisextension so that the die side connectors contact a landing on thesocket. This landing has a connection area 56 raised above the recess toconnect to the low level data signaling pins of the package. The set ofdata connectors may reside on one or more sides of the recess. As shownin FIG. 7, the data connectors are all around the periphery of therecess. The low level data signals are carried through the socket to aPCB (not shown) to which the socket is mounted.

The connections may take any of a variety of different types asdescribed above for mounting the package to the PCB and the socket maybe attached to the PCB in any of a variety of different ways. Socketsare commonly attached to PCBs is with reflow solder balls and SMT.Packages are commonly attached to sockets using pin grid arrays and landgrid arrays, however other technologies may be used for bothconnections. The socket may have a lever 57, lock or cover to secure thepackage in place. No connections for power are shown as these may bemade directly to the package. In an alternative embodiment, the socketmay be provided with a connector to a power source and a correspondingconnector to a land side or edge mounted power connector on the package.

In FIG. 6, the socket 63 has a hole 65 rather than a recess as in FIG.5. The hole allows the die 61 and cover 64 to extend through the socket,either to rest near the PCB or to be aligned with a hole in the PCB asshown e.g. in FIG. 4. Similar connectors 66 may be provided around theperiphery of the hole for the low level data signals and similarprovision may be made for a power supply which may be mounted directlyto the package as shown also in FIG. 4. A locking lever 67 is providedto hold the package in place, although other mechanisms may be usedinstead.

FIG. 7 shows a computer system suitable for use with the die and packagedescribed above. While embodiments of the present invention may beadapted for application on a great number of different ICs, the presentexample is described in the context of a microprocessor packagesupported by a chipset. In this example, the computer system may includea socket 161 for the CPU (Central Processing Unit) coupled to a chipsetcomponent 111 such as a Memory Controller Hub (MCH) chip. The MCH chipfunctions as part of a supporting chipset for the CPU. The MCH chip iscoupled to a main memory 167, such as DRAM and to a graphics controller141.

As shown in FIG. 5, the CPU socket 161 has a central opening 140 toreceive the package cover or the IHS for the package. This opening mayalso extend through the motherboard as well as the socket. An openingthrough the motherboard allows a heat sink to be mounted to the oppositeside of the motherboard as shown in FIGS. 3 and 4. As described above,the motherboard may also be adapted to receive the CPU package directlywithout using a socket. The sockets of FIGS. 4 and 5 are constructed toallow the package to be removed and replaced easily without soldering.

The socket also has a set of connectors 146 to couple low level signalsto the CPU. In the example of FIG. 5, these low level signals areprimarily coupled to the Host Controller 111. The connectors may alsoinclude power connectors or, alternatively, a separate power cable 147may be provided to provide power to a power supply mounted to the CPUpackage. Such a power cable may connect to a power supply 27, 47 asshown in FIGS. 2 and 4. Any of the connectors described above may beused in any of the illustrated embodiments including pin grid arrays,ball grid arrays, land grid arrays, surface mount, solder reflow balls,elastomer with conductive columns, and more.

The MCH chip 111 is also coupled to an ICH (Input/Output controller hub)chip 165. The ICH chip offers connectivity to a wide range of differentdevices. Well-established conventions and protocols may be used forthese connections. The connections may include a LAN (Local AreaNetwork) port 169, a USB hub 171, and a local BIOS (Basic Input/OutputSystem) flash memory 173. A SIO (Super Input/Output) port 175 mayprovide connectivity for a keyboard, a mouse, and any other humaninterface devices.

The ICH may also provide an IDE (Integrated Device Electronics) bus forconnections to disk drives 187, 189 or other large memory devices. Themass storage may include hard disk drives and optical drives. A PCI(Peripheral Component Interconnect) or PCI-X (PCI-Express) bus 191 maybe coupled to the ICH to allow a wide range of devices and ports to becoupled to the ICH. The architecture of FIG. 5 allows for a wide rangeof different functions and capabilities. The specific details of anyimplementation will depend on the particular application. The CPU, MCH,ICH, LAN port USB hub, BIOS, SIO port, IDE and PCI buses may all becarried on a single motherboard of the computer system. Any one or moreperipheral devices may also be carried on the motherboard. The computersystem may be adapted for use in many different applications includingoffice productivity, communications, entertainment, music and videoproduction or manufacturing.

Although the description of the various embodiments refers primarily tousing die side connectors to attach an integrated circuit package to asocket or a PCB, the various embodiments may also be used with othertypes of packages, interposers, PC boards or other electronic circuithousings. The various embodiments may be used with various types ofelectronic assemblies, and are not to be limited to use with integratedcircuit packages.

In addition, the various embodiments may be used with a number ofdifferent types of packages and packaging technologies, for example,organic or ceramic packages, and technologies such as land grid array(e.g., organic LGA), pin grid array (e.g., plastic PGA or flip chipPGA), ball grid array (e.g., μBGA, tape BGA, plastic BGA, flip chip BGAor flip chip tape BGA), and beam lead.

It is to be appreciated that a lesser or more complex semiconductordevice, integrated circuit, package, socket, connector, VRM, or PCB thanthe examples described above may be preferred for certainimplementations. Therefore, the configurations may vary fromimplementation to implementation depending upon numerous factors, suchas price constraints, performance requirements, technologicalimprovements, or other circumstances. Embodiments of the invention mayalso be applied to other types of systems that use different devicesthan those shown in the Figures.

In the description above, numerous specific details are set forth.However, embodiments of the invention may be practiced without thesespecific details. For example, well-known equivalent materials may besubstituted in place of those described herein, and similarly,well-known equivalent techniques may be substituted in place of theparticular techniques disclosed. In other instances, well-knowncircuits, structures and techniques have not been shown in detail toavoid obscuring the understanding of this description.

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described, but may be practiced withmodification and alteration within the spirit and scope of the appendedclaims. The description is thus to be regarded as illustrative insteadof limiting.

1. An apparatus comprising: a package substrate having a land side andan opposite die side; a first set of low level signal connectors on thedie side to connect to an IC to be carried by the package; a second setof low level signal connectors on the die side to connect to externalcomponents; a set of high power connectors on the land side to connectto a power supply; and a power supply connected to the land side of thepackage.
 2. The apparatus of claim 1, wherein the second set ofconnectors connect to a printed circuit board.
 3. The apparatus of claim1, wherein the second set of signal connectors connect to a socket. 4.The apparatus of claim 1, wherein the second set of signal connectorscomprise solder balls.
 5. The apparatus of claim 1, wherein the secondset of signal connectors comprise pins of a pin grid array.
 6. Theapparatus of claim 1, wherein the power supply comprises a voltageregulator module.
 7. The apparatus of claim 1, further comprising acooling subsystem coupled to the package opposite the land side of thesubstrate.
 8. The apparatus of claim 1, further comprising a packagecover to form an enclosure for the IC, wherein the first set ofconnectors is inside the enclosure and the second set of connectors isoutside the enclosure.
 9. The apparatus of claim 1, further comprising acooling device attached to the package cover.
 10. An apparatuscomprising: a package substrate having a land side and an opposite dieside; a first set of low level signal connectors on the die side toconnect to an IC to be carried by the package; a second set of low levelsignal connectors on the die side to connect to external components; acooling subsystem on the die side of the substrate to thermally coupleto the IC; and a heat spreader thermally coupled to the IC and attachedto the land side of the package substrate.
 11. The apparatus of claim10, further comprising a beat radiator thermally coupled to the heatspreader.
 12. The apparatus of claim 10, further comprising a printedcircuit board coupled to the set of connectors, the printed circuitboard further defining an opening and wherein the cooling subsystemextends through the opening.
 13. The apparatus of claim 10, furthercomprising a power supply mounted to the land side of the packagesubstrate to power the IC.
 14. The apparatus of claim 10, furthercomprising a package coupled to the package substrate to protect andcarry the microprocessor, the package having: a set of external dataconnectors on a first side of the package to communicate with the firstset of signal connectors; and a set of external power connectors on asecond side of the package opposite the first side of the package tocommunicate with the second set of signal connectors.
 15. The apparatusof claim 14, wherein the first side of the package is a die side of thepackage and the second side of the package is a land side of thepackage.
 16. The apparatus of claim 14, wherein the external dataconnectors are on the die side of the package substrate.
 17. Theapparatus of claim 14, further comprising a package cover attached tothe package substrate on the die side of the package and wherein thefirst and second sets of signal connectors are inside the package coverand the external power connectors are outside the package cover.
 18. Theapparatus of claim 14, further comprising a socket for carrying thepackage, the socket comprising: a structure to accommodate a die side ofthe package; and a set of data connectors on the periphery of thestructure to carry data signals to and from the die side of the package.19. The apparatus of claim 18, wherein the structure comprises a closedrecess.
 20. The apparatus of claim 19, wherein the set of dataconnectors are elevated from a bottom of the closed recess.
 21. Theapparatus of claim 18, wherein the structure comprises an opening. 22.The apparatus of claim 21, wherein the opening is adapted to align withan opening in a PCB to which the socket is to be mounted.